Method and apparatus for laser micromachining a conical surface

ABSTRACT

Embodiments of the present invention are directed to methods and systems for micromachining a conical surface. In one embodiment, such a system may include a rotating platform for receiving a long line of laser illumination, a mask having a predetermined pattern comprising a sector of a planar ring, the mask being positioned on the rotating platform, a workpiece stage having a rotational axis for rotating a removably-affixed workpiece comprising a conical surface, wherein the sector comprises the planar image of the conical surface, an excimer laser for producing a laser beam, a homogenizer for homogenizing the laser beam in at least a single direction, at least one condenser lens, a turning mirror and at least one projection lens.

CLAIM TO PRIORITY

The present applications claims priority under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 60/632,745, filed Dec. 2, 2004, theentire disclosure of which is herein incorporated by reference.

FIELD OF THE INVENTION

Embodiments of the present invention are directed to methods, devicesand/or systems in the field of micromachining, and more particularly inthe field of laser micromachining.

BACKGROUND OF THE INVENTION

Laser micromachining is a method by which material is removed from anobject (workpiece) to produce a product, utilizing the laser lightenergy. The laser light energy enables the material of the workpiece tobe ablated via either or both of thermal or chemical action.

Ablating a particular pattern in a workpiece may be accomplished usingmask-projection. In mask-projection, laser light is directed upon a maskand the image of it then projected onto the workpiece, irradiating thesurface with laser light energy according to the pattern of the mask.The pattern is reproduced on the surface of the workpiece.

Although it may be possible to micromachine non-planar surfaces (e.g.,curved surfaces, and the like), such micromachining is difficult toaccomplish at higher speeds/throughputs. Generally, only planar surfacesare capable of being micromachined quickly using, for example, amask-projection system. Thus, it would be an improvement in the existinglaser micromachining systems and methods to be able tolaser-micromachine conical surfaces (for example) in a high speed andefficient manner.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to lasermicromachining apparatuses/systems and/or methods thereof. Specifically,some embodiments of the invention include a laser micromachiningapparatus for copying an image of a planar mask onto a surface of aconical workpiece. In one embodiment of the invention, this may beaccomplished by rotating the mask and the cone synchronously.

Some embodiments of the present invention enable high-speed machining byprojecting a long-line of illumination along a conical surface all atonce with a large-field imaging lens.

Accordingly, in one embodiment of the invention, a system formicromachining a conical surface is provided and may include a rotatingplatform for receiving a long line of electromagnetic radiation, a maskhaving a predetermined pattern comprising a sector of a planar ring, themask being positioned on the rotating platform and a workpiece stagehaving a rotational axis for rotating a removably-affixed workpiece. Theworkpiece may include a conical surface, and the sector comprises theplanar image of the conical surface.

In another embodiment of the invention, a method for imaging a conicalsurface of a workpiece may be provided and may include directing anirradiating beam of electromagnetic radiation at a mask. The mask mayinclude a planar surface of a sector of a ring and a predeterminedpattern thereon and the ring sector may correspond to an unwrapped areaof a conical surface of a workpiece. The method may further includeproducing, as a result of the irradiating beam interacting with themask, an image field for projection on the conical surface of theworkpiece, projecting the image field onto the conical surface of theworkpiece, rotating the mask about an axis, wherein the axis comprisesthe center of the ring, and synchronously rotating the conical surfaceof the workpiece about a second axis, the second axis being the axis ofthe conical surface.

Embodiments of the present invention are directed to methods and systemsfor micromachining a conical surface. In one embodiment, such a systemmay include a rotating platform for receiving a long line of laserillumination, a mask having a predetermined pattern comprising a sectorof a planar ring, the mask being positioned on the rotating platform, aworkpiece stage having a rotational axis for rotating aremovably-affixed workpiece comprising a conical surface, wherein thesector comprises the planar image of the conical surface, an excimerlaser for producing a laser beam, a homogenizer for homogenizing thelaser beam in at least a single direction, at least one condenser lens,a turning mirror and at least one projection lens.

Still other embodiments of the invention may include computerapplication programs and computer readable media having an applicationprogram and/or computer instructions provided thereon for controllingsome of the embodiments of the invention for micromachining a conicalsurface.

These and other embodiments, advantages and objects of the inventionwill be more apparent with reference with the following detaileddescription and attached drawings, a brief description of which is setout below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an optical system for imaging on aconical surface according to some embodiments of the present invention.

FIG. 2 is a schematic of the relationship between a planar mask and aconical workpiece according to some embodiments of the presentinvention.

FIG. 3 is a block diagram of a laser micromachining system according tosome of the embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 illustrates one embodiment of a system 100 according to thepresent invention for imaging on a conical surface. As shown, a lasersource 101 directs a laser beam 102 into a beam expander 103. After thebeam expander, the resultant beam may be sent through a homogenizerand/or condenser lens(es) 104. The homogenizer may comprise thosehomogenizers as disclosed in co-owned and co-pending U.S. patentapplication publication no. 20040223330, entitled, “Methods andApparatuses for Homogenizing Light”, the entire disclosure of which isherein incorporated by reference.

A field lens 105 receives the homogenized/condensed beam, which collectsthe light for illuminating the mask 107. The mask pattern is preferablya representation of the unwrapped image 202 of a cone, which correspondsto a conical surface 204 of a cone 206 of a workpiece to be machined. Asshown in FIG. 2, the unwrapped image 202 may be a planar surface thatforms a sector 208 a ring.

While the present invention is illustrated with the use of a laser,other devices for generating a beam of electromagnetic energy (e.g.,x-ray) may also be used with embodiments of the present invention.

The mask 107 is preferably positioned in an open aperture, motorizedrotary device. The open aperture, motorized rotary device rotates mask107 about a center of rotation 210 as shown in FIG. 2 (i.e., center ofring). As shown in FIG. 2, a laser field generated by optics of thesystem (i.e., beam expander 103, condenser lens 104 and field lens 105)may be projected onto the mask 107. The laser field is preferably along-line field (i.e., a rectangular field), having short and long axes,but may comprise other shapes (e.g., elliptical, square, triangular, andother polygonal shapes). In long-line field embodiments, upon the longline field encountering the surface for machining, a short axis of thelong-line field may be oriented substantially perpendicular (preferablyperpendicular) to the conical workpiece axis (i.e., the vertex of thecone 206).

The long-line field projected onto the mask produces a long-line laserimage field which is then directed, via turning mirror 108, ontoprojection lens 109. The projection lens then projects the long-lineimage field onto the workpiece, the focusing of which may beaccomplished using adjuster device 110 (e.g., along a “Z” axis). In someembodiments, the turning mirror may be connected to at least one motoror other actuator(s) (e.g., piezo-based actuator) familiar to those ofskill in the art, which may enable the mirror to pivot about one or moreaxes, to impart other directional control onto the beam. In otherembodiments, the tuning mirror (as well as other components of theoptical system) may not include motor(s)/actuator(s), and may be rigidlyaffixed in a single position after setup.

The focusing adjuster device 110 may comprise a motor (rotary or linear)(or other actuator device), which may move lens 109 along a single(preferably) axis (e.g., Z axis). Movement may be established via a rackand pinion gear arrangement, when using, for example, a rotary electricmotor, or via direct connection of the lens or lens frame to the forceror platen of a linear motor.

The laser image field produced by the projection of the laser light ontothe mask, is then focused on the workpiece 112. Adjuster stages 113 and114 may be provided (e.g., “X” and “Y” adjuster stages), and may beinitially configured so that the laser image field is projected on thecorresponding area of the workpiece prior to machining. One of skill ofthe art will appreciate that in some embodiments of the invention, thepositions of adjusters 113 and 114 need not be adjusted once theirpositions are established during an initial setup. In such embodiments,the conical workpiece need only be rotated about an axis. As shown inFIG. 1, the axis of rotation of the conical workpiece (for example) isaxis 112 a.

FIG. 3 illustrates a block diagram of some of the embodiments of thepresent invention. As shown, a controller may be used to at least oneof, setup, initiate, control and complete the laser micromachining of aworkpiece. The controller may be an analog or digital control device,and is preferably a computer (e.g., personal computer operating anapplication program for controlling one or more of the components ofsystem 100). For example, the controller may be connected (througheither wireless or wired connection) to at least one of and preferablyseveral of: the laser/beam source (e.g., power, intensity), andmotors/actuators for: controlling beam expansion or consolidationdevices (e.g., beam expander 103, homogenizer 104, condenser lenses, andthe like), the open aperture-motorized rotary mask stage, the turningmirror 108, the focusing “Z” adjuster 110, the “X” adjuster stage 113,the “Y” adjuster stage 114 and the motorized rotary workpiece stage 111.In addition, position sensors may be positioned on all components andfed into the controller to provide (preferably) real-time feedback onthe positions and/or status of the components of the system.

Accordingly, the system may be operable for micromachining a workpieceupon performing at least several (and preferably all) of the following:

-   -   setup of a workpiece in the motorized workpiece stage 111;    -   alignment of the adjuster stages 113, 114;    -   positioning of turning mirror 108;    -   positioning of the mask 107 with the open aperture-motorized        rotary stage 106;    -   positioning of on or more of: the laser beam 101, the beam        expander 103, the homogenizer 104, condenser lenses and field        lens(es); and    -   focusing of the laser image field via focusing adjuster 110 such        that the laser image field is projected onto a substantially        correct corresponding portion of the conical surface of the        workpiece for machining.

Accordingly, after initial setup, and after the light source is switchedon, the mask may be rotated around axis 210 while synchronously rotatingthe conical workpiece around axis 212. By synchronously rotating themask from one side of the ring sector to the other and rotating the conearound its axis 212, for a full rotation, the entire pattern of the maskmay be imaged to the conical surface of the workpiece.

In some embodiments, the mask and the workpiece may be rotated inopposite directions since, in some embodiments, the projection lensinverts the image of the mask. Thus, if the mask is rotated clockwise,the conical workpiece is rotated counterclockwise (and visa-versa).

The homogenizer 104 may include a long line homogenizer to achieveuniform illumination (see U.S. published patent no. 20040223330).Although in some embodiments, the depth of focus of the imaging systemand the curvature of the cone may limit the width of the line.

In some embodiments, the mask pattern may be purposely distorted withastigmatic distortion—i.e., different magnification in the X and Ydirections along the conical axis to account for the variable radiusalong the conical surface. Alternatively, instead of creating thepurposeful distortion on the mask, the optical/projection system mayalso create a similar astigmatic distortion to achieve the same result.

To that end, with regard to the above-noted embodiments, it ispreferable that the long line of illumination include a narrow line—ifthe illumination line is too wide (according to some embodiments), theastigmatic distortion intentionally created by the mask or by the opticsmay blur the image on the workpiece. Thus, illuminating only asufficiently narrow line effectively eliminates the effect of theastigmatism. For example, when machining a conical workpiece of about 25mm in size, having conical surface of about 20 mm in length and havingdiameters of about 2 mm and about 10 mm, a width of a narrow line may beabout 1 mm.

However, the mask and the workpiece in some embodiments may be imagedwithout astigmatism distortion. In such embodiments, the magnificationvalues are preferably the same in both the X and Y directions.Therefore, when both the mask and the workpiece are rotated, theillumination line may be wider, and the illumination width is onlylimited by depth of focus on the curved surface. Thus, the process forthese embodiments may be faster by rotating both the mask and theworkpiece.

Having now described a few embodiments of the invention, it should beapparent to those skilled in the art that the foregoing is merelyillustrative and not limiting, and it should be understood that numerouschanges in creating and operating such systems and methods may beintroduced without departing from the true spirit of the invention asdefined in the appended claims.

1. A system for micromachining a conical surface comprising: a rotatingplatform for receiving a long line of electromagnetic radiation; a maskhaving a predetermined pattern comprising a sector of a planar ring, themask being positioned on the rotating platform; and a workpiece stagehaving a rotational axis for rotating a removably affixed workpiececomprising a conical surface, wherein the sector comprises the planarimage of the conical surface. 2-19. (canceled)
 20. An applicationprogram operational on a computer for enabling a method for imaging aconical surface of a workpiece, the method comprising: directing anirradiating beam of electromagnetic radiation at a mask, wherein themask includes a planar surface of a sector of a ring and a predeterminedimage thereon, the ring sector corresponds to an unwrapped area of aconical surface of a workpiece; producing, as a result of theirradiating beam interacting with the mask, an image field forprojection on the conical surface of the workpiece; projecting the imagefield onto the conical surface of the workpiece; rotating the mask aboutan axis, wherein the axis comprises the center of the ring;synchronously rotating the workpiece about a second axis, the secondaxis corresponding to the conical surface of the workpiece. 21.(canceled)